A construction machine, such as a hydraulic shovel, generally includes an engine as a motor, rotates at least one variable capacity type hydraulic pump by using the engine, and drives a hydraulic actuator by pressurized oil discharged from the hydraulic pump to perform a required operation.
When a sudden load generated by the hydraulic pump is transmitted to the engine in the construction machine, the engine may transmit currently generable torque information to a hydraulic pump control unit, and the hydraulic pump control unit may control a response to a torque limit to the sudden load in real time. Since the limit of a torque increase of the hydraulic pump is generally determined according to a predetermined test regulation, when a load is generated under another environment condition is generated during an actual operation of the construction machine, the appropriate torque limit responding control cannot be performed.
To this end, a technology for performing a minimum torque control of the hydraulic pump based on a target engine speed, and limiting a torque increase of the hydraulic pump based on a predetermined torque increase rate from a moment, at which the operating device is operated, to a predetermined time ΔT2 when a time of a non-operation state of an operation device of the construction machine elapses a predetermined time ΔT1 has been suggested.
The related art is a technology for limiting a torque of the hydraulic pump in order to prevent an engine speed from being decreased due to a sudden load generated at a moment when the operating device of the construction machine is operated in the non-operation state. That is, when a duration time of the non-operation state is larger than the predetermined time ΔT1, the hydraulic pump control unit controls a torque control valve of the hydraulic pump so that the hydraulic pump may maintain a minimum pump torque. In this case, when the operating device is suddenly operated, and a maintenance time of the urgent operation is smaller than a predetermined maintenance time ΔT2, the hydraulic pump control unit maintains the minimum pump torque. After the maintenance time of the urgent operation elapses the predetermined maintenance time ΔT2, the hydraulic pump control unit controls a torque of the hydraulic pump not to be increased to a maximum pump torque according to a target engine speed at a time similar to a general engine speed control, and controls the torque of the hydraulic pump to be increased at a decreased speed according to a predetermined torque increase rate K.
As described above, in the related art, information about a current state of the engine is not received from an engine control unit, but a quantitative numerical value for a reaction of the engine is derived by a method, such as a standard load test, and a pump torque control for limiting a pump torque increase rate of the hydraulic pump is performed based on the derived quantitative numerical value. When load follow-up performance of the engine is changed due to various environmental changes (temperature, humidity, atmospheric pressure, and the like) generable during an actual operation of the construction machine, a torque limit of the hydraulic pump is excessive or too little, so that a problem may occur in that the load is not appropriately matched between the engine and the hydraulic pump. In order to prevent the inappropriate load matching, various test environments need to be included in a process of the standard load test, and the like. The various test environments require many calculation loads from the hydraulic pump control unit, and as a result, a product development period is increased and product cost is increased.
Further, an engine performance characteristic indirectly recognized through a pump load torque by the method, such as the standard load test, in the related art is inappropriate to match a load between the engine and the pump. An engine speed behavior characteristic measured by the method for the standard load test and the like may be different from engine performance calculated during the actual control of the engine control unit. That is, since only limited information among engine information required for controlling the pump is used in the related art, the pump control unit cannot accurately recognize a state of the engine, and thus, an engine-pump matching control may not be smoothly performed.